Laser hair removal: Comparison of long-pulsed Nd : YAG, long-pulsed alexandrite, and long-pulsed diode lasers

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Laser Hair Removal: Comparison of Long-Pulsed Nd:YAG,
Long-Pulsed Alexandrite, and Long-Pulsed Diode Lasers
NAVID BOUZARI, MD,
n
HOSSEIN TABATABAI, MD,
n
w
ZAHRA ABBASI, MD,
w
ALIREZA FIROOZ, MD,
n
AND YAHYA DOWLATI,MD,PHD
n
n
Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, and
w
Mehregan
Skin Laser Center, Tehran, Iran
BACKGROUND. Advances in laser technology over the past
several years have led to the development of numerous lasers
for the treatment of unwanted hair. Laser wavelength is a key
factor influencing treatment efficacy and complication rates.
OBJECTIVE. To compare the efficacy and safety of laser hair
removal using three different laser systems.
METHODS. A retrospective study of 805 consecutive laser-
assisted hair removal treatments, conducted on 75 patients by
means of either a long-pulsed Nd:YAG, a long-pulsed alexan-
drite, or a long-pulsed diode laser is reported. All patients were
evaluated at least 3 months after the last treatment, and their
present conditions were compared with the 1st-day photographs.
RESULTS. The mean hair reduction was 42.4%, 65.6%, and
46.9% in Nd:YAG, alexandrite, and diode lasers, respec-
tively. When the number of treatment sessions was taken into
account, the efficacy of alexandrite and diode lasers was not
significantly different, whereas both systems were more
efficacious than Nd:YAG. Neither of the laser systems showed
better results for a particular skin type. The occurrence of side
effects was not significantly different between three laser
systems.
CONCLUSION. Both long-pulsed alexandrite and long-pulsed
diode laser systems are effective in the treatment of unwanted
hair, and they are more efficacious than Nd:YAG laser.
N. BOUZARI, MD, H. TABATABAI, MD, Z. ABBASI, MD, A. FIROOZ, MD, AND Y. DOWLATI, MD, PHD HAVE
INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS.
LASER-ASSISTED HAIR removal has been recently
introduced as the treatment of choice for the reduction
of unwanted hair. Hair removal lasers work based on
the theory of selective photothermolysis.
1
Currently,
several lasers are available for the treatment of
unwanted hair. Laser wavelength is a key factor
influencing treatment efficacy and complication rates
because different lasers have specific absorption
properties.
2
However, there is paucity in our knowl-
edge about the optimal laser systems and parameters
for a permanent and effective hair reduction in each
skin type. The purpose of this study is to compare the
efficacy of three different hair removal laser systems
(long-pulsed Nd:YAG, long-pulsed alexandrite, long-
pulsed diode) in various skin types, as well to
determine the frequency of side effects induced by
each laser system.
Methods
A retrospective study of 805 consecutive laser-assisted
hair removal treatments was conducted on 75 con-
senting patients (1 male and 74 females) with 181
anatomic areas over 18-month period. Patients were
excluded if the period of last treatment session to time
of investigation was less than 3 months. Treatment
sites included chin (67), upper lip (55), and periauri-
cular (34), and neck (25). Fitzpatrick skin types I–V
were represented. The distribution of skin types in
different laser systems is shown in Table 1.
Patients were instructed to avoid sun tanning and to
cease using other hair removal methods on the
treatment sites at least 1 month before the commence-
ment of the laser treatment. The treatment sites were
shaved before each treatment session. No specific
preoperative topical anesthesia was used. Postopera-
tive care included sun avoidance (at least 3 days),
avoiding harsh soaps, scrubs, facial peels, or topical
acne therapies. A low-potency topical corticosteroid
was used after the treatment session in the case of
erythema or perifollicular edema (once or twice in the
treatment day).
Hair removal was performed by means of either a
long-pulsed Nd:YAG, long-pulsed alexandrite, or
long-pulsed diode laser. The choice of laser system
employed was based on each laser’s availability and
was randomly allocated rather than on distinct patient
selection criteria. In five patients, more than one type
of laser system was employed because of unavailability
r2004 by the American Society for Dermatologic Surgery, Inc. Published by Blackwell Publishing, Inc.
ISSN: 1076-0512/04/$15.00/0 Dermatol Surg 2004;30:498–502
Address correspondence and reprint requests to: Navid Bouzari, MD,
1175 NE Miami Gardens Dr. 708E, NMB, FL 33179.

of the laser system, which had been employed in a
previous session(s). These patients were allocated in a
separate group (combination group); however, their
results were not entered in the analysis and just
reported. The treatment session interval was delivered
on a monthly basis. The long-pulsed Nd:YAG laser
system (Yaglase plus; Depilase Ltd., London, UK) was
used at a 1064-nm wavelength. Fluences ranging from
40 to 55 J/cm
2
(mean SD, 45.9 4.9 J/cm
2
) were
delivered through different spot sizes ranging from 6 to
8 mm. Pulse durations ranged from 25 to 32 ms
(mean SD, 27.7 2.0 ms) at a repetition rate of
1 Hz. The long-pulsed alexandrite system (Aphrodite,
Quanta system, Italy) was used at a 755-nm wave-
length to deliver fluences ranging from 15 to 25 J/cm
2
(mean SD, 20.4 2.2 J/cm
2
) through 8- and 10-
mm spot sizes. The pulse duration ranged from 10 to
20 ms (mean SD, 12.3 2.1 ms) at 1 Hz. The
pulsed diode laser system (Lightsheer XC; Coherent,
Santa Clara, CA) at an 800-nm wavelength was used
at fluences ranging from 25 to 40 J/cm
2
(mean SD,
33.7 4.7 J/cm
2
) with a 9-mm spot size and 1 Hz,
whereas pulse durations ranged from 10 to 30 ms
(mean SD, 20.3 5.5 ms). The Nd:YAG and the
alexandrite lasers were equipped with a dynamic
cryogen device; however, the contact sapphire window
was employed for cooling in the diode laser.
Photographs were taken with a digital camera at the
first session before laser treatment. Before each
subsequent treatment, an experienced dermatologist
evaluated the patients and, if needed, adjusted laser
system parameters (fluence, spot size, or pulse width)
up or down. A comparison of the 1st-day photograph
with present patients’ status was the method of
investigator evaluation. For hair counting of the chin
and the upper lip, all of the hairs of the right side of the
photograph and patient were counted to obtain the
percentage of hair reduction. For hair counting of
the periauricular and neck region, a 4-cm
2
area on the
right side was located on the photograph, and then
hair counting was performed to obtain the percentage
of hair reduction. To be assured that the 4-cm
2
area on
the photograph and patient are of the same dimension,
the size of an area on the face of patient (e.g., the
distance between two nevi) was measured. Then the
photograph was zoomed in or out to reach the same
size. Patients were questioned on the effects of the
previous treatment before each treatment session.
Patients rated their satisfaction on a 4-point scale
(hair reduction of less than 25%, 25% to 50%, 50%
to 75%, more than 75%). The treatment was con-
sidered efficacious if both patient and investigator
signified a more than 50% hair reduction. In six cases,
the pretreatment photographs did not have an accept-
able quality; thus, in these cases, only the patients’
ideas were taken into account. Patients were also
questioned about the adverse effects (pain, blister or
erosion, hyperpigmentation, hypopigmentation, and
folliculitis). Terminalization was another adverse effect
that was defined as conversion of vellus-type hairs to
terminal hairs in the treatment area after the laser
procedure.
Statistical analyses were undertaken by using SPSS,
version 10. A p value of 0.05 or less was considered
significant. All of the statistical analyses have been
done with 95% confidence interval, when appropriate.
Values were tested for normality, and when appro-
priate, independent sample t-test or nonparametric
equivalents have been used. Spearman ror Kendall’s
tau-b has been used to show correlations.
The investigational protocol was approved by the
institutional review board of the Center for Research
and Training in Skin Diseases and Leprosy.
Results
The mean hair reduction between three laser systems
was different (po0.0001). It was 42.4%, 65.6%, and
46.9% in Nd:YAG, alexandrite, and diode lasers,
respectively. Mean SD number of laser treatment
sessions was 2.6 1.2 for patients treated with diode,
significantly lower than those who were treated with
Nd:YAG (5.5 2.2 sessions) or alexandrite (5.2 
2.1 sessions, po0.0001). There was a positive correla-
tion between hair reduction and the number of treat-
ment sessions (r50.461, po0.001). When the efficacy
was compared between laser systems in number-
matched sessions, there was no statistically significant
difference between diode and alexandrite. The efficacy
of laser systems in each skin type is shown in Table 2.
There was no significant difference between skin types
in response to treatment.
Side effects were observed in 44.7% of study
population. Pain was the most frequently reported
side effect (25 patients), and hyperpigmentation (9),
blister or erosion (8), terminalization (8), folliculitis
Table 1. Distribution of Different Skin Types in Laser
Systems (Number of Patients) (p 50.416)
Skin Type Nd: YAG Alexandrite Diode Combination
n
Total
I–1––1
II – 6 4 1 11
III 5 11 17 2 35
IV 4 10 9 2 25
V21––3
Total 11 29 30 5 75
In this group, more than one type of laser systems was used for each patient.
Dermatol Surg 30:4:April 2004 BOUZARI ET AL.:LASERHAIRREMOVAL 499

(4), and hypopigmentation (2) were the other reported
ones (Table 3). It should be noted that some patients
reported more than one problem. The overall occur-
rence of side effects in patients who were treated with
Nd:YAG (45%), alexandrite (40%), and diode (46%)
was not different. The frequency of side effects
between different skin types was not statistically
different (Figure 1). The fluence of Nd:YAG laser
was significantly higher in those patients who reported
treatment pain (po0.0001), and the fluence of
alexandrite laser was higher in those who experienced
hyperpigmentation (po0.05) or blister or erosion
(po0.0001). No association was found between the
occurrence of side effects and diode laser fluence.
Among 13 treatment areas in patients who received
combination laser therapy in 12 cases, the treatment
was efficacious. Hyperpigmentation was the most
common side effect (seven patients). Pain (three),
blister (four), and hypopigmentation (one) were the
other reported side effects.
Discussion
Multiple lasers and light sources are currently avail-
able for hair removal, and more than 100 studies of
efficacy and safety have been conducted. However,
most of the studies have been conducted with different
parameters, anatomic areas, number of treatments,
treatment intervals, and most importantly, different
investigators and counting techniques.
3
In addition, in
most of those studies, one laser system was evaluated,
and studies comparing the efficacy of different laser
systems are infrequent.
We did not find studies comparing the efficacy of
these three laser systems (Nd:YAG, alexandrite,
diode); however, those comparing the efficacy of the
1-ns Q-switched Nd:YAG, alexandrite, and ruby have
found the former to be the least efficacious.
4,5
It should
be noted that in their studies the Nd:YAG lasers were
not long pulsed. In another study that employed a
long-pulsed Nd:YAG and a diode laser in darker skin
patients, both lasers showed similar efficacy.
6
Although alexandrite laser seemed to be more effica-
cious than diode laser in our study, more treatment
sessions in alexandrite group may explain its better
outcome in comparison to diode group. This explana-
tion is supported by a lack of difference between the
results of alexandrite and diode when the number of
sessions was taken into account. Earlier studies also
reported equivalent clinical and histologic responses
using a long-pulsed alexandrite and a long-pulsed
diode.
7,8
A review of the previous studies that
evaluated each laser system separately shows that the
success rate of our laser systems is almost compatible
with theirs. Goldberg et al.
9
reported long-pulsed
Nd:YAG laser hair reduction to be 45% in axilla and
24% in bikini region. The previous reports on the
efficacy of long-pulsed alexandrite laser were 74% to
78% hair reduction,
10–12
and the reported hair
reduction of long-pulsed diode lasers ranged between
22% and 59%.
3,13–15
Five of our patients underwent laser therapy with
different laser systems. The treatment outcome in this
group was the best; however, we did not find similar
studies in this regard, and we do not know whether
this method of treatment is scientifically prudent.
However, one explanation could be that the longer
wave lengths may be more helpful in damaging deeper
hairs that are not much darker than the skin, whereas
shorter wave lengths are better to use for more
superficial targets;
16
thus, the use of two different
laser systems may increase the chance of destroying
both deep and superficial targets.
Table 2. Efficacy of Laser Systems in Each Skin Type
(Number of Efficacious Cases/Total)
Skin type Nd:YAG Alexandrite
n
Diode
n
I – 1/1 –
II – 13/18 4/8
III 3/11 17/24 20/42
IV 5/10 20/26 10/21
V 2/4 2/3 –
Total 10/25 53/72 34/71
Number of treatments with alexandrite is higher than the diode in all skin types.
Table 3. Side Effect Rates in Laser Systems (Number of Patients)
Side Effects Nd:YAG (n 511) Alexandrite (n 529) Diode (n 530)
Overall Occurrence
(Including Combination) (n 575)
Pain 36% (4) 30% (9) 33% (11) 33% (25)
Blister or erosion 18% (2) 3% (1) 12% (4) 10% (8)
Hyperpigmentation 9% (1) 6% (2) 12% (4) 12% (9)
Hypopigmentation 0 3% (1) 0 2.5% (2)
Folliculitis 0 6% (2) 6% (2) 5% (4)
Terminalization 27% (3) 12% (4) 3% (1) 10% (8)
500 BOUZARI ET AL.:LASER HAIR REMOVAL Dermatol Surg 30:4:April 2004

There are limited reports with regard to comparing
the efficacy of laser systems in different skin types.
Patients with darker skin types present a greater
treatment problem, and the goal for these patients is
to deliver the highest fluence to the hair follicles
without causing injury to the epidermis.
10
However,
we did not find hair regrowth to be more prevalent in
darker skin-type patients. In addition, neither laser
system seemed to have advantages over the others
according to a particular skin type in our study.
Nonetheless, there are some reports that suggest
particular laser systems for different skin types: The
Nd:YAG laser at 1064 nm wavelength is supposed to
be ideal for treating patients with darker skin
types.
5,17,18
It should be noted that our judgment
about the laser systems is regardless of the evaluation
of ‘‘number of treatments’’ in each skin type, which
could not be done because of the paucity of samples
when allocated in number-matched subgroups of
different skin types.
Consistent with our study, numerous articles have
suggested that multiple laser treatments yield more
effective results.
19–22
On the other hand, Sadick et
al.
23
did not find a positive correlation between hair
reduction and number of treatments.
According to previous studies,
10,11,13,24,25
the most
common side effects of laser treatment are erythema
and perifollicular edema, which were not evaluated in
our study. After these, treatment pain is the most
frequently reported side effect.
15,24
Hyperpigmenta-
tion rate has also reported to be 8% to 30%, and its
prevalence in our study (10%) is compatible with
Nanni et al., Eremia et al., and Rogachefsky et al.
studies.
10,15,24
There is not much work done on the comparison of
side effects between laser systems. However, in a study
that compared the side effects of 1-ns Q-switched
Nd:YAG, alexandrite, and ruby, the side-effect profiles
were similar, although there were some differences; for
example, postoperative pigmentary alterations were
less common in Nd:YAG, whereas folliculitis was
more common in that laser system.
24
In that study, Q-
switched Nd:YAG laser was suggested as the ideal
laser for darker skin-type patients. Nonetheless, we did
not find any laser system to have advantageous to
others in this regard.
Conclusion
The 755-nm alexandrite and the 800-nm diode laser
have almost equal efficacy, whereas the Nd:YAG laser
is the least efficacious. Neither laser system has
advantage to the others for a particular skin type.
The ‘‘number of treatments’’ was a confounding factor
in our study, which affected our results, and its
statistical exclusion in the future studies will be of
paramount importance.
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0
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